Filter materials and uses thereof

ABSTRACT

The present invention relates to filter materials comprising cellulose acetate and polylactide in a ratio of about 95:5 to about 75:25 by weight, and to filters ( 2 ) or filter elements comprising such filter materials. The invention also relates to smoking articles ( 1 ) comprising the filter materials, filters ( 2 ) or filter elements.

FIELD

The present invention relates to filter materials. More specifically,the invention relates to filter materials that may be used to filtersmoke, such as the tobacco smoke generated by smoking articles. Theinvention also relates to filters or filter elements comprising thefilter materials, as well as to smoking articles comprising the filtermaterials, filters or filter elements.

BACKGROUND

A variety of materials have been suggested as filter materials forcigarette smoke. Cellulose acetate tow is a commonly used filtermaterial in filters for smoking articles, where it contributes to theselective removal of particulate phase and selected semi-volatilecompounds. However, cellulose acetate tow can be expensive compared tosome other filter materials which may be used. It is also desirable toseek to use materials in filters which are from a sustainable source.Nevertheless, cellulose acetate is the established tow material forcigarette filters and, for consumer acceptance and potentially for anyregulatory acceptance, any replacement filter material would have tohave similar filtration properties and would have to provide filteredsmoke with similar taste and mouthfeel characteristics.

SUMMARY

According to a first aspect of the present invention there is provided afilter material comprising cellulose acetate and polylactide in a ratioof about 95:5 to about 75:25 by weight.

In a second aspect of the present invention, a filter or filter elementfor a smoking article is provided, comprising the filter materialaccording to the first aspect.

In a third aspect of the present invention, a smoking article isprovided, comprising the filter material according to the first aspector comprising the filter or filter element according to the secondaspect.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that aspects of the invention may be more fully understood,embodiments thereof will now be described by way of illustrative examplewith reference to the accompanying drawings.

FIG. 1 is a schematic side view of a smoking article including a filteraccording to embodiments of the invention.

FIG. 2 is a schematic cross-sectional illustration of the arrangement ofthe CA tow and PLA fibres in a filter or filter element according to oneembodiment.

FIG. 3 is a schematic cross-sectional illustration of the arrangement ofthe CA tow and PLA fibres in a filter or filter element according toanother embodiment.

FIG. 4 is a schematic cross-sectional illustration of the arrangement ofthe CA tow and PLA fibres in a filter or filter element according to afurther embodiment.

FIG. 5 is a schematic cross-sectional illustration of the arrangement ofthe CA tow and PLA fibres in a filter or filter element according to ayet further embodiment.

FIG. 6 is a schematic cross-sectional illustration of the arrangement ofthe CA tow and a non-woven sheet of PLA in a filter or filter elementaccording to one embodiment.

FIG. 7 is a schematic cross-sectional illustration of the arrangement ofthe CA tow and a non-woven sheet of PLA in a filter or filter elementaccording to an alternative embodiment.

FIG. 8 is a schematic cross-sectional illustration of the arrangement ofthe CA tow and a non-woven sheet of PLA in a filter or filter elementaccording to a yet further embodiment.

FIG. 9 is a schematic axial cross-sectional illustration of a smokingarticle with a filter comprising filter material according to anotherembodiment of the invention.

FIGS. 10 to 16 provide graphs showing experimental data from the studiesset out in the Examples.

DETAILED DESCRIPTION

In some embodiments, the invention relates to the combination ofcellulose acetate and polylactide to provide filter material. It may bedesirable for the filter material to be suitable for use in a smokingarticle, and/or for use in a filter or a filter element, such as may beused in a smoking article.

In some embodiments, the filter material comprises cellulose acetate andPLA in a ratio of between about 75:25 and about 95:5 by weight, a ratioof between about 75:25 and about 90:10 by weight, a ratio of betweenabout 75:25 and about 85:15 by weight, or in a ratio of about 80:20 byweight.

The experimental data, which is discussed in detail in the Examples,demonstrates that filter materials of the present invention exhibit goodfiltration characteristics. It is also shown that the properties of afilter made from this material may be adjusted to produce desired smokeyields and filtration efficiency.

Cellulose Acetate

Cellulose acetate (CA) is an organic ester which is used for manyindustrial applications in the form of films and fibres. CA is derivedfrom cellulose using the acetylation process and its main properties areits hardness, good resistance to impact, high shine, transparency,pleasing texture, lack of static electricity and resistance tohydrocarbons. CA has been reported to be potentially biodegradable. Thebiodegradation rate of CA may depend on its degree of acetyl-groupsubstitution (DS). As the DS of CA decreases, the biodegradation rateincreases. CA with a DS of less than 2.1 is considered to bebiodegradable, whilst CA with a DS above 2.1 is only poorly or slowlybiodegradable.

The cellulose acetate (CA) used in filter materials for inclusion insmoking articles frequently has a degree of substitution (DS) of around2.5. Whilst this relatively high DS means that CA is poorly degradable,this DS is selected as it renders the CA soluble in solvents such asacetone. Solvent solubility of the CA allows the material to beprocessed in useful ways, such as solvent film casting and solvent fibrespinning, which is the process used to form the fibres of the celluloseacetate tow conventionally used in the filters of smoking articles.

CA for use in smoking article filters may be treated with plasticizers.This involves applying the plasticizer (usually in liquid form) to thesurface of the CA fibres, for example by spraying the liquid plasticizeron to the CA tow. The plasticizer acts by binding adjacent fibres to oneanother at their contact points, thereby affording the filter rodssufficient hardness for cigarette manufacture and use. Thus, althoughthe materials added to CA in this way are generally referred to asplasticizers, they are really acting as binders or hardeners rather thanas plasticizers. Suitable plasticizers for this use include triacetin(glycerin triacetate), TEC (triethyl citrate) and PEG 400 (low molecularweight polyethylene glycol). Plasticized cellulose acetate tow is alsoknown to improve the selective removal of some semi-volatile compoundsfound in smoke (e.g. phenol, o-cresol, p-cresol and m-cresol). For thiseffect, it is considered to be necessary for the plasticizer to bepresent on the surface of the CA fibres.

Because of the fibre-binding effect of plasticizers, CA filtersgenerally include less than 10% plasticizer and frequently less than 7%by weight. It has been found that including plasticizer in greateramounts than this has a detrimental effect on the cellulose acetate tow,causing holes to be formed.

The types of CA discussed above may be used in the present invention.The cellulose acetate may be in the form of fibres, for example in theform of a fibrous tow. Cellulose acetate with a degree of substitutionof about 2.1 to about 2.5, or of about 2.5 may used in some embodiments.

In some embodiments, the CA included in the filter materials may bemodified in order to provide or enhance beneficial properties, such asdegradability, filtration and/or the taste characteristics of thefiltered smoke.

For instance, cellulose acetate tow may be made from compositionscomprising a blend of CA and a plasticizer, in which the plasticizer isintegrated within the structure of the CA and is retained. The blend maybe formed by solvent blending, wherein the CA and plasticizer aresoluble in acetone or other suitable solvent and the blend compositionis formed from the solution and comprises an intimate blend of CA andplasticizer. Alternatively, the CA and plasticizer may be melt blended.

In another instance, the cellulose acetate tow may be made from acomposition comprising a blend of cellulose acetate (which may be CAblended with a plasticizer) and a water soluble polymer, said blendbeing optionally compatibilized. In some embodiments, such compositionsmay be water dispersive and/or biodegradable. Suitable water solublepolymers include polyvinyl alcohol (PVOH), carboxymethyl cellulose(CMC), hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC),methyl cellulose (MC) and ethyl cellulose (EC), hydroxyethylmethacrylate (HEMA), xanthan and pullulan, or blends thereof. Suitablecompatibilizers include grafted copolymers, such as PLA-graftedwater-soluble polymers, and include reactive compatibilizers such asmaleic anhydride-grafted polylactide (MA-g-PLA).

Polylactide

Poly(lactic acid) or polylactide (PLA), is a biodegradable andbiocompatible polymer. It is derived from renewable resources (e.g.,corn, wheat, or rice) and it is biodegradable, recyclable, andcompostable. In addition, PLA exhibits excellent processability. It canbe processed by injection moulding, film extrusion, blow moulding,thermoforming, fibre spinning, and film forming.

The polylactide (PLA) used in the present invention may be produced bydifferent synthetic methods, such as ring-opening polymerization oflactide or direct condensation polymerization from lactic acid. Any PLAgrade can be selected for use in this invention, and the molecularweights of the PLA may vary depending on the desired properties and use.In some embodiments, poly(L-lactide) (PLLA) may be preferred due to itscrystallinity, which is beneficial for the production of fibres.

The filter material of the present invention may comprise PLA in variousforms, including, for example, in the form of fibres, in the form of afibrous tow and/or in the form of one or more non-woven sheet materials.The PLA may be present in the filter material in more than one form.

PLA Fibres

Where the PLA is provided in the form of fibres, the polylactide fibresmay, in one embodiment, consist essentially of polylactide.

Fibres may be manufactured from PLA in various ways including, forexample, a solvent spinning process or a melt extrusion process.

In some embodiments, the filter material comprises cellulose acetatefibres and PLA fibres in a ratio of between about 75:25 and about 95:5by weight, a ratio of between about 75:25 and about 90:10 by weight, aratio of between about 75:25 and about 85:15, or a ratio of about 80:20by weight.

PLA Sheet

In some embodiments of the invention, the PLA filter material may be inthe form of a non-woven sheet. Non-woven sheet materials may be used asfilter materials in smoking articles, for example in the form of crimpedor gathered sheets.

Non-woven materials are broadly defined as sheet or web structuresbonded together by entangling fibres or filaments mechanically,thermally or chemically, or by a combination of two or more of these.They tend to be flat, porous sheets that are made directly from separatefibers. They are not made by weaving or knitting and do not requireconverting the fibers to yarn.

Thus, in one embodiment, a filter material according to the presentinvention may comprise CA tow and one or more PLA non-woven sheets. Thetwo materials may be arranged to ensure that the resultant plug offilter material exhibits sufficient hardness and structural integrity toenable it to be incorporated into a smoking article using theconventional high-speed manufacturing machinery.

Sheet materials can have certain drawbacks when used as the sole form offilter material. In order to attain the desired structural rigidity whenconstructing a filter element from non-woven sheet materials, the filtermaterial must be very densely packed and this means that these filterelements have quite different properties to those made of fibrous tow.They exhibit a greater resistance to the flow of smoke, resulting in apressure drop which is higher than that of a conventional celluloseacetate tow filter, requiring the user to draw harder on the smokingarticle. Perhaps more significantly, the smoke drawn through such filtermaterial has been found to have different taste characteristics comparedto the smoke drawn through conventional cellulose acetate filtermaterial. What is more, filter elements comprising non-woven sheetmaterials or paper as the filter material have been shown to exhibitsignificantly less selective removal of particulate phase and selectedsemi-volatile compounds than conventional cellulose acetate tow filtermaterials.

In one embodiment where a non-woven PLA sheet material is included inthe filter material, the sheet material includes one or moreplasticizers, including PEG and/or triacetin and/or TEC. For example,the sheet material may include PEG and one or both of triacetin and TEC.In one embodiment, the polyethylene glycol may be liquid at roomtemperature, such as PEG 400. In another embodiment, the polyethyleneglycol may be a high molecular weight polyethylene glycol, such as onewhich is solid at room temperature. Such polyethylene glycols includePEG 600 and higher, and preferably PEG 1000 and higher. These particularpolyethylene glycols are attractive as they are solid or semi-solid atroom temperature and so their addition will not compromise thestructural integrity of the non-woven sheet material. Additives whichare liquid at room temperature can in some circumstances adverselyaffect the structural integrity and strength of a filter element wherethe filter material is a non-woven sheet material, for example they maysoften the non-woven material. For that reason, there may be a limit onthe amount of such additives which can be included whilst stillretaining the required rigidity and strength of the sheet material.

Indeed, rather than weakening the non-woven sheet filter material, theuse of a high molecular weight polyethylene glycol may actually increasethe structural integrity and rigidity of the filter material. Thisprovides further flexibility when forming a filter or filter elementwith regard to the amount of filter material required to achieve thedesired hardness and rigidity. This in turn would allow the manufacturerto adjust the pressure drop of the filter element. This would allow afilter or filter element to be designed having properties which closelyresemble those of conventional CA filter elements.

In addition, the selective removal of semi-volatile compounds providedby the addition of the PEG to the filter material is proportional to theamount of PEG included. The flexibility to add greater amounts of PEG,including high molecular weight PEG, means that the ability of thefilter material to selectively remove semi-volatile compounds may beadjusted to a desirable level.

In one embodiment of the present invention, the PEG is included in or onthe non-woven sheet material in an amount of up to 30%, preferably up to20%, and more preferably of 5-10% by weight of the sheet. These figuresare determined by comparing the dry weight of the sheet without the PEGto the weight of the sheet including the PEG additive.

The addition of TEC and/or triacetin has a different effect on thenon-woven sheet material. These additives have been surprisingly foundto have a beneficial effect on the taste and odour of the smoke which isdrawn through the filter element. A common criticism of filter materialsother than CA is that they tend to adversely affect smoke taste. Thetriacetin and TEC have different effects on the smoke's tastecharacteristics and the two additives may be added in differing amountsin order to produce a desirable smoke taste profile.

In conventional cellulose acetate tow used in filter material, theamount of triacetin or TEC which can be included is limited by theeffect that these additives have on binding the fibres of the fibrousmaterial, with amounts of triacetin exceeding about 7% causing holes tobe formed in the cellulose acetate material. In contrast, the amount ofTEC and triacetin which may be included in or on the non-woven sheetmaterial is not so limited. Indeed, where PEG is also included which issolid at room temperature, the effect of these liquid additives inmaking the sheet material soggy is minimised and up to 30% by weight ofTEC and/or triacetin may be included, although amounts of up to 20% orup to about 12% by weight of the sheet material may be preferred. Thesefigures are determined by comparing the dry weight of the sheet materialwithout the additive to the weight of the sheet material including theadditive.

Further additives can be incorporated into or onto the non-woven sheetmaterial, including tobacco extracts, glycerine, menthol, carbon fibres,carbon particles, and the like. Such additives can be incorporated intothe sheet material during its manufacture, or applied to the materialafter manufacture is complete.

In certain embodiments, filter materials may comprise non-woven sheetmaterials having a thickness greater than about 0.05 mm, preferably fromabout 0.06 mm to about 0.08 mm. The non-woven PLA filter materials mayhave a basis weight of about 15 g/m² to about 60 g/m², preferably about20 g/m² to about 45 g/m².

The non-woven PLA sheet may be manufactured by any known process. Forexample, spunbond sheets are made by forming a web from extruded, spunfilaments and then bonding the fibres. During the web laying process,the fibres may be separated by air jets or electrostatic charges. Thebonding imparts strength and integrity to the web and may be carried outby applying heated rolls or hot needles to partially melt the polymerand fuse adjacent fibres together. Spunlacing is another process whichuses high-speed jets of water to strike a web so that the fibers becomeknotted with one another.

Filters and Filter Elements

Filter elements and filters according to the present invention comprisethe filter material according to the first aspect of the invention.These filter elements and filters may be incorporated into smokingarticles.

Thus, the filter elements and filters in accordance with the inventionmay comprise filter material which comprises cellulose acetate and PLAin a ratio of between about 75:25 and about 95:5 by weight, a ratio ofbetween about 75:25 and about 90:10 by weight, a ratio of between about75:25 and about 85:15 by weight, or in a ratio of about 80:20 by weight.

The cellulose acetate may be in the form of a tow. The PLA may be in theform of fibres, in the form of a fibrous tow and/or in the form of oneor more non-woven sheet materials.

Referring to FIG. 1, for purpose of illustration and not limitation, asmoking article 1 according to an exemplary embodiment of the inventioncomprises a filter 2 and a cylindrical rod of smokeable material 3, suchas tobacco, aligned with the filter 2 such that one end of the smokeablematerial rod 3 abuts the end of the filter 2. The filter 2 is wrapped ina plug wrap (not shown) and the smokeable material rod 3 is joined tothe filter 2 by tipping paper (not shown) in a conventional manner. Thefilter 2 is substantially cylindrical and has a mouth end 4 and asmokeable material end 5. The filter 2 comprises a plug of filtermaterial according to the present invention, comprising celluloseacetate fibres 6 and polylactide.

The plug of filter material preferably has a size and shape suitable tomatch the size and shape of the rod of smokeable material to which it isto be attached in a finished smoking article.

Although the illustrated smoking article 1 includes a filter 2 having asingle filter element or segment comprising a blend of cellulose acetateand a water soluble polymer as described herein, other arrangements arepossible. For instance, the filter 2 can comprise multiple segments,such as 2, 3 or more segments, with some or all of the segmentscomprising filter material according to the invention.

Many different filter arrangements for smoking articles arecontemplated, including composite filters wherein the filter comprises aplurality of separate filter elements or sections with differentfiltering capacities, and/or comprising different materials, such asdifferent filter materials and additives, such as adsorbents andflavourants. As used herein, the term “flavourant” refers to materialswhich, where local regulations permit, may be used to create a desiredtaste or aroma in a product.

Where the filter material comprises PLA in the form of fibres, the CAtow and PLA fibres may be provided in the form of a homogenous mixture,with the PLA fibres dispersed throughout the fibres of the CA tow.

In alternative embodiments, the PLA fibres are arranged in a tow and thefilter material comprises one or more zones of PLA tow and one or morezones of CA tow. Some of the possible arrangements of these zones areillustrated in FIGS. 2 to 5.

In one embodiment, as illustrated in FIG. 2, the filter plug 10 is madeup of PLA tow 12 arranged as a central core, surrounded by an outerlayer of CA tow 11, the filter material in turn being surrounded by aplug wrap 14. In an alternative embodiment (not shown in the figures),the central core is made up of CA tow and the surrounding material isPLA tow made up of PLA fibres.

In other embodiments, as illustrated in FIGS. 3 and 4, the PLA tow isprovided in multiple regions. In FIG. 3, the PLA tow 12 is provided asmultiple zones which are surrounded by CA tow. The zones are shown ashaving a circular cross-section, but other shapes may be used. Thenumber, size and the shape of the zones may vary. The zones may extendlongitudinally along the entire length of the filter plug, or only alongpart of it. In FIG. 4, the PLA tow 12 is provided in radially extendingzones, with CA tow 11 positioned between said zones.

In a further possible configuration, as illustrated in FIG. 5, the PLAtow is provided in the form of a layer of tow 12 which is embeddedwithin the CA tow 11 so that the layer of PLA tow 12 is arranged in aspiral configuration, wrapped around the longitudinal axis of thefilter. A layer of PLA tow may be incorporated into the filter plug inother ways.

According to some embodiments, the filter material comprises PLA in theform of a non-woven sheet material in combination with CA tow. Some ofthe possible arrangements of this combination of PLA sheet and CA toware illustrated in FIGS. 6 to 8.

In one embodiment, as illustrated in FIG. 6, the filter plug 10 is madeup of PLA sheet 13 packed to form a central core, surrounded by an outerlayer of CA tow 11. The zones are shown as having a circularcross-section, but other shapes may be used. In an alternativeembodiment, as shown in FIG. 7, the central core is made up of CA tow 11and the surrounding material is formed from one or more PLA sheets 13.

Various alternative arrangements of the sheet material and tow are alsoenvisaged. For example, as shown in FIG. 8, the PLA sheet material 13may be arranged in a spiral configuration, wrapped around thelongitudinal axis of the filter. Interspersed between the wrappings ofthe sheet material 13, which may be made up of one or more sheets, is CAtow 11.

By way of further example, as shown in FIG. 9, the PLA and CA in thefilter material of the invention are arranged within the filter “inseries”. In the figure, the filter 2 is made up of two sections ofsegments, one comprising CA tow 21 and the other comprising PLA 22, inthe form of tow, non-woven sheet, or a combination thereof. Part of theadjacent smokeable material rod 3 is also shown. The CA tow may bepositioned adjacent to the rod of smokeable material, with the PLA atthe mouth-end of the filter, as illustrated in FIG. 9. In an alternativeembodiment, these positions could be reversed. The lengths of thesegments of sections are different in the figure, to reflect the ratioof CA to PLA being between 95:5 and 75:25.

However, in some embodiments, the PLA and CA of the filter materialaccording to the invention are both provided in the same section orsegment of a filter or filter element.

It is possible to make filters and filter elements from filter materialsas described herein using conventional processes, techniques andapparatus.

Some filter elements may exhibit a pressure drop of greater than about40 mm of water at an airflow rate of 17.5 cm³/s per 0.1 g of filtermaterial. They may also exhibit a filtration efficiency for particulatematter of mainstream tobacco smoke of less than about 15% per 0.1 gramof filter material.

In one embodiment the filter material comprising CA tow and PLA may bethe sole filter material in the filter element or filter.

In another embodiment a filter element comprising the CA tow and PLA maybe part of a larger filter. In other words, the filter element may bepart of a composite or multi-component filter. The filter elements ofthe composite filter may be arranged longitudinally of one another withthe end of each filter element abutting the next. The composite filtermay have 2, 3, 4 or more distinct or discrete sections.

A composite or multi-component filter may comprise one or more filterelements according to the present invention. Where there is more thanone filter element according to the present invention in the compositefilter, suitably the filter elements may be positioned longitudinallynext to one another or be separated by another filter element.

Where the filter element is used in a composite filter, the one or moreother sections of the composite filter may comprise a biodegradablefilter material, such as crepe, crimped or gathered paper material. Theone or more other sections may optionally comprise one or moreadditives, such as adsorbent or flavouring materials.

In a yet further alternative, the composite filter may comprise asection which forms a cavity containing granular material.

In addition, the pressure drop and/or mechanical filtration efficiencyof the filter plug sections can be selected to achieve the desiredsmoking mechanics and filtration characteristics as may be required withthe specific product design desired.

In a composite filter arrangement the pressure drop of the filtrationmaterial plugs/sections may be varied.

A portion of the filter element and/or the composite filter comprisingsaid filter element may comprise a catalyst. Advantageously the catalystfacilitates the conversion of carbon monoxide (CO) to carbon dioxide(CO₂) in the vapour phase of the smoke. It is much by preference thatthe catalyst is highly selective for carbon monoxide. Preferably thecatalyst may be one of the group consisting of transition metal oxides,silica, alumina, zeolites, impregnated carbon, for example, carbonimpregnated with metals.

In some embodiments, the tobacco-rod end portion of the filter mayinclude a cavity containing an adsorbent and/or catalyst or,alternatively, may comprise a smoke filtration material having anadsorbent and/or catalyst dispersed therein. Advantageously theadsorbent is capable of retaining at least a portion of the vapour phaseof smoke.

Smoking Articles

Smoking articles of the present invention comprise a filter materialaccording to the first aspect of the present invention. The filtermaterial may be present in the form of a filter element or filteraccording to the invention, attached to a rod comprising a smokeablefiller material (e.g. tobacco). The smoking article may be a cigarette.

As used herein, the term “smoking article” includes smokeable productssuch as cigarettes, cigars and cigarillos whether based on tobacco,tobacco derivatives, expanded tobacco, reconstituted tobacco or tobaccosubstitutes and also heat-not-burn products.

Thus, smoking articles may comprise filter material which comprisescellulose acetate and PLA in a ratio of between about 75:25 and about95:5 by weight, a ratio of between about 75:25 and about 90:10 byweight, a ratio of between about 75:25 and about 85:15 by weight, or ina ratio of about 80:20 by weight.

The cellulose acetate may be in the form of a tow. The PLA may be in theform of fibres, in the form of a fibrous tow and/or in the form of oneor more non-woven sheet materials.

The filter element and/or filter comprising said filter element may beattached to a wrapped rod of smokeable filler material by conventionaltipping overwrap to form a smoking article. The tipping overwrap may beventilating or non-ventilating overwrap.

The smokeable filler material may be tobacco material or a tobaccosubstitute material. Preferably the smokeable material is a tobaccomaterial. Suitably the tobacco material comprises one or more of stem,lamina, and tobacco dust. The tobacco material may comprise one or moreof the following types: Virginia or flue-cured tobacco, Burley tobacco,Oriental tobacco, reconstituted tobacco. According to some embodiments,the smokeable material comprises a blend of tobacco material. Forexample, the smokeable material may comprise 10-80% Virginia tobacco,10-60% Burley tobacco, 0-20% Oriental tobacco, 0-20% reconstitutedtobacco and 0-30% expanded tobacco.

In some embodiments, the smoking material of smoking articles comprisinga filter material according to the invention and/or filter or filterelement according to the invention may comprise or consist of cuttobacco, a proportion of which tobacco may be expanded tobacco. Thesmoking material may comprise reconstituted tobacco or tobaccosubstitute material.

EXAMPLES

Experiments have been carried out to investigate and illustrate thefilter processing of non-woven PLA, combination of non-woven PLA withcellulose acetate (CA) tow and the smoke chemistry of the differentfilter variants and the use of three filter plasticizers.

The non-woven PLA was produced using the spun bond process. The basisweight of the sheet is 30 gsm with a thickness is 180 μm.

1. Filter Manufacture

The non-woven PLA was converted into filter rods using the paper filterprocess for pure non-woven PLA and using the Combined Material Filter(CMF) filter process in case of filters made from a blend of non-wovenPLA and CA.

Table 1 shows the characteristics of the 132 mm filter rods (withoutplasticizer) manufactured from non-woven PLA.

TABLE 1 Sheet width Rod Circ. Hardness* PD Filter Ref. (mm) weight (g)(mm) (%) (mm WG) D633/4382D 200 0.89 24.30 84.35 237 D633/4382C 240 1.0624.30 88.43 384 D633/4382E 250 1.10 24.30 90.33 431 D633/4382B 260 1.1424.30 90.08 495 D633/4382A 300 1.27 24.30 93.42 707 *Filtrona hardnessmeasurement.

FIG. 10 shows the variation of the pressure drop (PD) as a function ofthe sheet width. The filter rod length was 132 mm. FIG. 11 shows therelationship between the pressure drop and the rod weight. The filterrod length was 132 mm. The “Corrected PD” means that the pressure dropis calculated for a circumference of 24.30 mm in case the initial filtercircumference is slightly different from 24.30 mm.

The results show a linear relationship between pressure drop and theweight of the filter rods. A comparison between the capability curve ofthe non-woven PLA (FIG. 11) and those of CA tow (not shown here)indicates that for the same pressure drop the weight of the filter rodis much higher in case of non-woven PLA. The weight of filter rod (132mm) manufactured from a conventional CA tow is 807 mg.

The characteristics of the filter rods (132 mm length) manufacturedusing different plasticizers are summarized in Table 2 (TA=triacetin,PEG=poly(ethylene glycol) and TEC=triethyl citrate). The filter rodswere manufactured from non-woven PLA web with a width of 250 mm. Thehardness results show that none of the additives used act as a binder.The filter rod hardness decreases with increasing the amount of theadditives used (see Table 2).

TABLE 2 Loading Circ. Hardness* PD Filter Ref. Additive (% wt) (mm) (%)(mm WG) D633/4383A TA 4.0 24.30 89.98 447 D633/4383B TA 7.3 24.30 87.68452 D633/4383C PEG400 4.6 24.30 90.22 442 D633/4383D PEG400 8.7 24.3089.17 444 D633/4383E TEC 3.7 24.30 88.98 451 D633/4383F R TEC 8.5 24.3087.53 452 *Filtrona hardness measurement.

The characteristics of the filters (132 mm length) manufactured bycombining non-woven PLA and CA tow are summarized in Table 3. Thefilters where made using the Combined Materials Filter (CMF) process.The plasticizer used was triacetin (TA).

TABLE 3 Filter Reference Rod Parameters D645/4384C D645/4384A D645/4384BComposition: 75/25 47/53 35/65 CA/PLA (wt %) CA tow 2.5Y37 2.1Y22 6Y17PLA sheet width (mm) 55 115 145 Filter rod weight (g) 1.11 1.04 1.12 TAloading (mg/rod) 89.3 50.4 73.0 Circ. (mm) 24.09 24.24 24.48 Hardness*(%) 94.6 91.3 93.4 PD (mm WG) 758.3 577.2 370.1 *Filtrona hardnessmeasurement.

2. Cigarette Manufacture

Cigarettes were assembled using the filters mentioned in Tables 1 to 3without any major processing issues. A conventional CA tow was used asthe CA control.

3. Smoke Chemistry 3.1. Filtration Efficiency

In order to evaluate the filtration efficiency of the new filters andcontrol, cigarettes were smoked under the ISO regime with theventilation zone blocked. Table 4 summarizes the effect of pressure dropon the smoke yields of cigarettes with PLA filters (without additives)of different pressure drops and CA control.

TABLE 4 Filter pressure drop (mm WG) Smoke yield 41 71 94 123 CA control(66) NFDPM (mg/cig) 14.8 12.8 11.5 9.7 13.3 Nicotine (mg/cig) 1.1 0.90.8 0.7 1.1 CO (mg/cig) 13.3 13.6 13.0 12.6 14.0 Water (mg/cig) 4.1 3.22.5 1.7 4.5 Puff no. 8.5 8.3 8.4 8.0 8.7

Table 5 shows the smoke yields of cigarettes with PLA filters containingdifferent additives, compared to a conventional CA control. Theadditives were triacetin (TA), poly(ethylene glycol) (PEG) and triethylcitrate (TEC).

TABLE 5 Additive CA control Smoke yield 7.3% TA 8.7% PEG 6.4% TEC (8.6%TA) NFDPM (mg/cig) 13.6 12.9 11.8 13.3 Nicotine (mg/cig) 0.9 0.9 0.9 1.1CO (mg/cig) 14.7 13.9 12.4 14.0 Water (mg/cig) 3.9 2.5 2.7 4.5 Puff no.8.8 8.8 8.4 8.7

FIG. 12 shows the filtration efficiency results for PLA filters (withoutplasticizer) at different pressure drops. The results show for NFDPM theefficiency of the PLA filter became similar to the CA control around thePD of 71 mm WG.

FIG. 13 shows the filtration efficiency in the presence of differentadditives, using conventional CA as a control. The results indicate thatthe nature of the additive has a small effect on the NFDPM filtrationefficiency. The water filtration efficiency is significantly affected inthe case of PEG and TEC in comparison to TA. One possible explanation isthat the presence of these additives may affect the hydrophilicity ofPLA. The additives used do not show any significant effect on nicotinefiltration efficiency.

The smoke yields and the filtration efficiency in the case of filtersmanufactured using the Combined Materials Filter (CMF) process are shownin Table 6 and FIG. 14, respectively. The filter composition isexpressed as CA/PLA (w/w) percentage. The results show that the NFDPMfiltration efficiency is higher in the case where the filter composition(CA/PLA) is 47/53 and even higher where the composition (CA/PLA) is75/25. However, it should be noted that the pressure drop and filterweight of the CMF filters (Table 3) are higher in comparison to the CAcontrol (420 mm WG, 810 mg for the filter rod of 132 mm). (Filtercharacteristics are reported in Table 3.)

TABLE 6 Filter variant CMF CMF CMF PLA Control Smoke yield 35/65 47/5375/25 100% 100% CA NFDPM (mg/cig) 13.8 11.7 10.4 11.5 13.3 Nicotine(mg/cig) 1.0 0.9 0.8 0.8 1.1 CO (mg/cig) 12.4 13.2 12.5 13.0 14.0 Water(mg/cig) 3.0 2.9 2.0 2.5 4.5 Puff no. 8.6 8.3 8.6 8.4 8.7

3.2. Filtration Selectivity

In order to evaluate the filtration selectivity of the differentfilters, cigarettes were smoked under the ISO regime with ventilationblocked and Hoffmann analytes were measured under the same conditionsfor all the cigarettes. Only the phenolic compounds were considered inthis study.

Table 7 summarizes the effect of different additives in the PLA filteron the phenolic compound yields. (Filter characteristics are reported inTable 2.)

TABLE 7 Filter variant 7.3% 8.7% 6.4% CA control Constituent None TA PEGTEC (8.6% TA) Catechol (μg/cig) 47.9 52.7 49.5 44.8 55.8 Hydroquinone43.6 48.2 46.1 41.3 55.7 (μg/cig) m-Cresol (μg/cig) 5.5 4.8 3.9 3.3 3.0o-Cresol (μg/cig) 7.2 5.8 4.6 3.6 3.3 p-Cresol (μg/cig) 13.8 11.9 9.98.0 6.9 Phenol (μg/cig) 28.3 23.3 16.7 14.9 10.8 Resorcinol (μg/cig) 1.41.5 1.4 1.4 1.7 Puff no. 8.4 8.8 8.8 8.4 8.7

FIG. 15 shows the effect of additives on the filtration of the selectedphenols using a pure non-woven PLA filter as the control. The resultsare normalized to tar and expressed as a percentage difference with CAcontrol. The results show clearly a decrease of the cresols and phenolin comparison to the PLA filter without additive, especially for phenolswhen TEC is used. It appears that the PLA filter has certain selectivitytowards catechol, hydroquinone and resorcinol and there is no differencecompared to the CA control. Since these compounds are found in theparticulate phase, this result is consistent with particulate filtrationtheory.

In the case of CMF, the results show that blending CA with PLA enhancesthe filtration selectivity in comparison to 100% PLA filter and the bestresults for phenol selectivity were obtained for the filter with theCA/PLA composition of 75/25. Table 8 shows the phenols delivery usingCombined Materials Filter (CMF) compared to 100% PLA and a conventionalCA control. The filter composition is expressed as CA/PLA (w/w)percentage. (Filter characteristics are reported in Table 3.)

TABLE 8 Filter variant CMF CMF CMF PLA CA Constituent 35/65 47/53 75/25100% control Catechol (μg/cig) 62.3 52.8 49.3 47.9 55.8 Hydroquinone58.5 50.1 47.1 43.6 55.7 (μg/cig) m-Cresol (μg/cig) 3.6 3.0 2.2 5.5 3.0o-Cresol (μg/cig) 4.1 3.4 2.4 7.2 3.3 p-Cresol (μg/cig) 8.7 7.0 5.2 13.86.9 Phenol (μg/cig) 15.4 12.4 8.0 28.3 10.8 Resorcinol (μg/cig) 1.8 1.61.4 1.4 1.7 Puff no. 8.6 8.3 8.6 8.4 8.7

FIG. 16 shows the effect of the filter composition on the filtrationselectivity. The results are normalized to tar and expressed as apercentage difference with CA control. CA control is used as a baseline.

As set forth above, non-woven PLA can be processed into a cigarettefilter using the paper filter process and a combination of non-woven PLAand CA tow can also be combined to form filter material.

The capability curve shows that a wide range of filters can bemanufactured with different pressure drops depending upon the width ofthe material. The weight of the filter made from non-woven PLA is higherthan that made from CA tow with the same pressure drop. The additivesTA, PEG and TEC do not act as a binder to harden the non-woven PLA in afilter. However, TA, PEG, TEC can be used as an additive in the PLAfilter to enhance the filtration selectivity towards phenols.

The combination of CA tow with non-woven PLA gave some advantages incomparison to PLA filters such as increased hardness of the filter andincreased selective filtration of phenols.

For the avoidance of doubt, it is confirmed that any feature of theinvention discussed herein may be used in combination with any otherfeature. In particular, any feature in a claim may be used incombination with any other feature in a claim.

Embodiments described above are configured to comply with applicablelaws and/or regulations, such as, by way of non-limiting example,regulations relating to flavourings, additives, emissions, constituentsand/or the like.

Many other modifications and variations will be evident to those skilledin the art, that fall within the scope of the following claims.

1. A filter material comprising: cellulose acetate and polylactide in aratio of about 95:5 to about 75:25 by weight, the polylactide includingone of a fibrous polylactide tow and an at least one non-wovenpolylactide sheet.
 2. The filter material as claimed in claim 1, whereinthe cellulose acetate and polylactide are present in a ratio of about80:20 by weight.
 3. The filter material as claimed in claim 1, whereinthe cellulose acetate comprises cellulose acetate tow.
 4. The filtermaterial as claimed in claim 1, wherein the polylactide comprises afibrous polylactide tow.
 5. The filter material as claimed in claim 1,wherein the polylactide comprises at least one non-woven polylactidesheet.
 6. The filter material as claimed in claim 3, wherein thecellulose acetate tow includes a plasticizer.
 7. The filter material asclaimed in claim 1, wherein the polylactide includes a plasticizer. 8.The filter material as claimed in claim 6, wherein the plasticizer isselected from the group consisting of triacetin, triethyl citrate,polyethylene glycol.
 9. The filter material as claimed in claim 6,wherein the amount of plasticizer included in the filter material is 0to 20% by weight of the filter material.
 10. A filter element for asmoking article, comprising: filter material including cellulose acetateand polylactide in a ratio of about 95:5 to about 75:25 by weight, thepolylactide having one of a fibrous polylactide tow and an at least onenon-woven polylactide sheet.
 11. A smoking article comprising: a filtermaterial including cellulose acetate and polylactide in a ratio of about95:5 to about 75:25 by weight, the polylactide having one of a fibrouspolylactide tow and an at least one non-woven polylactide sheet.
 12. Thefilter material as claimed in claim 7, wherein the plasticizer isselected from the group consisting of triacetin, triethyl citrate,polyethylene glycol.
 13. The filter material as claimed in claim 7,wherein the amount of plasticizer included in the filter material is 0to 20% by weight of the filter material.
 14. The filter elementaccording to claim 10, wherein the cellulose acetate and polylactide arepresent in a ratio of about 80:20 by weight.
 15. The filter element asclaimed in claim 10, wherein the cellulose acetate comprises celluloseacetate tow.
 16. The filter element as claimed in claim 15, wherein thecellulose acetate tow includes a plasticizer.
 17. The filter element asclaimed in claim 10, wherein the polylactide includes a plasticizer. 18.The smoking article according to claim 11, wherein the cellulose acetateand polylactide are present in a ratio of about 80:20 by weight.
 19. Thesmoking article as claimed in claim 11, wherein the cellulose acetatecomprises cellulose acetate tow.
 20. The smoking article as claimed inclaim 11, wherein the polylactide includes a plasticizer.